Spiny rush (Juncus acutus)

Also known as: Sharp rush, Juncus, Spiky rush

Spiny rush is a clumping plant 1–2 m tall that has very sharp tips on the leaves and stems. It can outcompete native plants and injure people and animals.

Profile

How does this weed affect you?

Spiny rush:

• has very sharp points on the end of stems and leaves that can injure people and animals
• forms dense infestations that restrict the movement of people and animals including access to waterways
• outcompetes native plants
• is not eaten by livestock and further degrades pastures on poor soils
• provides habitat for pest animals such as rabbits.

 Spiny rush is a serious threat to coastal saltmarsh, which is an endangered ecological community in NSW.

What does it look like?

Sharp rush is a clumping perennial plant that grows in a dome shape. Usually it is 1- 1.2 m tall but occasionally can reach 2 m.

Stems and leaves

The flowering stems and leaves look very similar. The stems are 30-160 cm long and 2-4 mm in diameter and the flowers forms below the tip. The leaves are slightly smaller and have a yellow to golden brown sheath. Both stems and leaves are:

• dark green
• thin and cylindrical
• filled with pith
• stiff with very sharp pointed tips.

Flowers are:

• green, red or brown depending on age
• very small
• just below the tip of the stems in clusters with 1–6 flowers per cluster and 5–50 clusters per inflorescence
• present from spring to summer.

Fruit are:

• golden-brown to chestnut brown capsules
• 5–6 mm long
• oval shaped with 3 cells that contain many seeds.

Seeds are:

• 1–2 mm long
• oval or irregularly shaped with a papery tail at each end.

Roots are:

• shallow
• fibrous mats

 Spiny rush also produces short creeping underground stems called rhizomes.

Similar species

Spiny rush looks similar to many other Juncus species. In NSW there are 43 native juncus and 20 naturalised introduced species. Spiny rush's key feature is the very sharp pointed leaves and stems. 

 The native Sea rush Juncus kraussii  looks very similar but it only grows in coastal areas. Its stems and leaves are also sharp but not as sharp or as stiff as spiny rush. Native sea rush is more upright and vertical than the dome-shaped spiny rush. The capsule is smaller only up to 3 mm long. The seeds are also smaller (0.5-1.0 mm) and they do not have papery tails at each end.

Where is it found?

There are scattered infestation in many regions of NSW. The main infestations are in the Greater Sydney, Hunter, Murray and South East regions.

This plant is native to Southern Europe, the Mediterranean region and Western Asia.

What type of environment does it grow in?

Spiny rush grows in temperate climates. It tolerates soils with low fertility and saline soils. Plants can grow in shallow salty water. In NSW it has been found growing in:

• coastal areas including coastal saltmarsh
• swamps and wetlands
• degraded pastures
• mine tailings and dredge spoil
• roadside table drains in saline areas.

Maps and records

• Recorded presence of Spiny rush during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

By seed

Plants do not flower until they are two years old.  Mature plants can produce up to 4000 seeds per year and the seeds can remain viable after many years in the soil. Seeds are spread mainly by water. They are also moved by:

• wind,
• water birds
• in mud
• contaminated agricultural produce, vehicles and machinery.

By plant parts

Plants can grow from pieces of the crown or rhizomes. These can be spread by cultivation, earth-moving equipment and when contaminated soil is moved to a new area.

References

Brown, K., & Bettink, K. (2006). Biology of Sharp Rush,* Juncus acutus. In Managing Sharp Rush (* Juncus acutus), Proceedings of a workshop held at Wollaston College Conference Centre, Mt Claremont Perth, Western Australia. WA Department of Environment and Conservation.

Daly, T. (2013), Coastal saltmarsh. Primefact 1256, NSW DPI.

Identic Pty Ltd. and Lucid central (2016). Environmental Weeds of Australia Fact sheet: Juncus acutus Retrieved: 8 February 2023 from:  https://keyserver.lucidcentral.org/weeds/data/media/Html/juncus_acutus_subsp._acutus.htm

Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 8 February 2023 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Juncus~acutus

Sainty, G. R., & Jacobs, S. W. (2003). Waterplants in Australia (No. Ed. 4). Sainty and Associates Pty Ltd.

More information

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Control

Wear personal protective clothing to prevent injuries from the sharp stems and leaves when controlling this plant.

Mechanical removal

Dense infestations can be removed using cutters, graders or ploughs. Cultivation can also be effective but plants need to be collected and disposed of. Burning is an effective disposal method. Resow pastures or revegetate treated areas. Use salt tolerant species in saline areas. 

Herbicide

Wiping

Wiping can be used on spiny rush growing in crops or pastures. The wiper needs to be at least 10 cm higher than the crop or pasture and the spiny rush must be at least 15 cm higher than the crop or pasture. If plants have many dead leaves or stems it is best to slash first and then wipe when the spiny rush regrows to a suitable height.

Herbicide options

See Using herbicides for more information.

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Glyphosate 360 g/L (Weedmaster Duo)
Rate: 1 L of herbicide in 2 L of water
Comments: Apply by wiper application to actively growing plants. Wiper application should be a minimum of 10 cm above the crop or pasture and weeds should be at least 15 cm above the crop or pasture, See label for more instructions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Hunter	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023